Heparin, a natural sulphated polysaccharide, is an anticoagulant that belongs to the family of glycosaminoglycans. The anticoagulant activity of heparin is due to its ability to accelerate the inhibition of several proteases, particularly factor Xa and thrombin, in the blood coagulation cascade.
Heparin and heparin-derived drugs inhibit the activity of factor Xa by attaching to a specific binding domain of antithrombin (AT). Once heparin or heparin-derived drugs are attached to the specific binding domain of antithrombin, they induce a conformational change in antithrombin (AT). This conformational change in AT is responsible for inhibition of factor Xa. Investigations have shown that the lowest structural element capable of significantly binding AT, and inhibiting factor Xa, is a pentasaccharide.
The prototype of such conformational-change-inducing products is fondaparinux. Fondaparinux sodium (Arixtra™—GlaxoSmithKline) is the first of a new class of antithrombotic agents. It displays a half-life in rats of approximately one hour and of 17 h in human. It is given once a day to patients in need of an anticoagulant treatment. It is a chemically synthesised pentasaccharide mimicking the antithrombin binding site of heparin. It is a selective factor Xa inhibitor and thus an inhibitor of thrombin generation.
The synthesis of fondaparinux is long and complicated. Thus, with the aim of simplifying the chemistry while maintaining the same activity and pharmacokinetic profile, new series of pentasaccharides described in U.S. Pat. No. 5,543,403 or in WO 99/36428 have been designed.
U.S. Pat. No. 5,543,403 discloses synthetic pentasaccharides in which N-sulfate, N-acetate and hydroxyl groups are replaced by alkoxy, and O-sulfate groups. WO 99/36428 discloses similar synthetic pentasaccharides, the L-iduronic unit of which is locked in a 2S0 conformation, and the D-glucuronic unit E of which has eventually an ethyl group at position 5.
However, while the presence of alkyl groups on these pentasaccharides unit considerably simplifies their mode of preparation, it also increases the half-life making the clinical use problematic.
EP 2 074 131 also attempts to provide synthetic pentasaccharides. In this application, it was considered that the ability of the pentasaccharides to go through the intestinal barrier was important for an application as antithrombotics.
However, it appeared that many compounds disclosed by EP 2 074 131 also have a too long half-life.
The half-life of anticoagulant pentasaccharides, the time required to halve the plasma concentration of the drug, is a very important pharmacokinetic parameter. Indeed, it is sometimes necessary, e.g. in case of an haemorrhage, to switch off as quickly as possible the anticoagulant effect so that the haemorrhage can be stopped.
Suitable half-lives for an anticoagulant range from about 5 to about 20 hours in human, corresponding to 0.5 hour to about 3 hours in the rat.
Introduction of a biotin moiety on the pentasaccharide allows fast suppression of the anticoagulant activity through injection of avidin, a protein that strongly binds to biotin.
The biotin group (IUPAC name: 5-[(3aS,4S,6aR)-2-oxohexahydro-1H-thieno[3,4-d]imidazol-4-yl]pentanoic acid; also known as vitamin B7) represents the following group:

Such biotinylated pentasaccharides are known from EP 1 322 673. Avidin prevents the compounds from having their effect on their targets and accelerates their elimination. The anti-factor Xa activity of the biotinylated compounds of EP 1 322 673 is equivalent to the activity of their non-biotinylated counterparts.
Thus, it is possible to neutralize the anticoagulant activity of biotinylated compounds by administration of avidin which eventually allows using long half-life anticoagulant pentasaccharides.
However, the enzyme biotinidase, that cleaves the amide bond at the carboxylate end of biotin, is present in blood plasma and could react with biotinylated compounds to de-biotinylate them. As a result, the de-biotinylated compounds are no longer neutralised by avidin while keeping their anticoagulant activity until they are physiologically washed out. This is a real problem because anticoagulant treatments can be given for long period of time and the de-biotinylated compound can accumulate in plasma. Therefore, it is still highly desirable to have biotinylated compounds with a short half-life to allow their immediate neutralization in case of emergency and to avoid their accumulation in plasma if they are de-biotinylated by biotinidase.
The authors of the present invention have surprisingly found that the half-life of alkylated/O-sulfated pentasaccharides can be modulated by varying the substituent groups of the D-unit.
Introducing an amino function at position 2 reduces the half-life.
Biotinylation of this 2 amino-function increases the half-life
Introducing one free hydroxyl function at the D-unit reduces the half-life.
A combination of these various observations allowed the authors to identify potent inhibitors of factor Xa biotinylated pentasaccharides with a short half-life.
Thus, one aim of the invention is to provide pentasaccharides, which are easy to synthesize and with a short half-life, and in particular biotinylated pentasaccharides.
Another aim of the invention is to provide biotinylated pentasaccharides with high anti-factor Xa activity, i.e. low value of IC50.
Therefore, all drawbacks of the prior art are overcome with the use of the compounds according to the invention, and more in particular the biotinylated ones.